1. Field of the Invention
The present invention is in the field of water wells, and specifically relates to a device that is installed underground in the well to deny access to lower portions of the well.
2. The Prior Art
A number of plugs, seals, locks, and wireline tools have been developed in the oil industry to solve various problems unique to that industry, but on close inspection it will be seen that none of these oil industry devices works in the same manner as the present invention. The present invention requires that the well have a plastic casing. Such casings are almost universally used in water wells, but are not used in oil and gas wells.
For example, in U.S. Pat. No. 3,812,911, Vann shows a retrievable plug that includes locking dogs that can be extended radially outwardly from a plug to engage a circumferential slot. Similarly, in U.S. Pat. No. 4,116,274, Rankin et al. show a wireline latching apparatus that also includes three arms that are pivotally mounted to the apparatus and that can be actuated to an open position in which they engage a downwardly facing shoulder in the casing.
In U.S. Pat. No. 4,058,162, Smith describes a well tool that can be locked within and sealed with respect to the bore of a well. The device has a threaded coupling at the top and a threaded member that operates locking dogs that engage the bore of the well.
In U.S. Pat. No. 4,411,314, Shearhart shows the use of a socket wrench at the lower end of a string of tubing for engaging a hexagonal nut located at the top end of a casing packer for the purpose of rotating the nut.
Thus, although the relevant technology was developed in the oil industry, it will be seen below that the present invention includes distinguishing structural features which adapt it for use in water wells.